looking for a book that stays with you long after it’s over

I’ve been in a bit of a reading slump lately and I’m looking for something that really pulls me in. I want a story that is so immersive that I forget I’m actually reading, with characters that feel like real people.

I really enjoy stories with high stakes, not necessarily "saving the world" stakes, but deeply personal ones. I love sharp, smart writing and a plot that keeps me guessing without being confusing.

What is the one book that completely changed how you look at the world?